Convective Cold Upper Hybrid Instabilities

Abstract

We present the results of a systematic parametric study of convective instabilities of the upper hybrid mode (based on the density of cold electrons) induced by a loss cone hot electron distribution. We have varied the hot and cold electron densities and temperatures and the slope of the hot electron loss cone distribution. We find that a theory with completely cold electrons cannot explain the observations of magnetospheric ‘3/2’ emissions. Finite cold electron temperature can induce non-convective instabilities, and in general, ensures large spatial growth rates, even when the temporal growth rates are small. The plasma can thus be significantly unstable, even for weak loss cone distributions. Finite cold electron temperature and the weak loss cone produce unstable frequency band widths in agreement with observations, when the convective growth rate is constrained to suit magnetospheric scale lengths.